revert 'Made it possible to drop null placeholders from array output.'

revert ae3c7a7aab

include/json/writer.h

@@ -158,13 +158,6 @@ public:
 
   void enableYAMLCompatibility();
 
-  /** \brief Drop the "null" string from the writer's output for nullValues.
-   * Strictly speaking, this is not valid JSON. But when the output is being
-   * fed to a browser's Javascript, it makes for smaller output and the
-   * browser can handle the output just fine.
-   */
-  void dropNullPlaceholders();
-
 public: // overridden from Writer
   virtual std::string write(const Value& root);
 
@@ -173,7 +166,6 @@ private:
 
   std::string document_;
   bool yamlCompatiblityEnabled_;
-  bool dropNullPlaceholders_;
 };
 
 /** \brief Writes a Value in <a HREF="http://www.json.org">JSON</a> format in a